please help im scared

Hi, I had sex with a person with whom I have casual sex. We used a condom but when he pulled it out, we realized it broke. We quickly bought the plan b (I would say it was about half an hour after it happened). We are not sure if sperm fell inside, but I bought it anyway to prevent it. I am very scared and anxious, I really don't want to get pregnant. I know it's impossible to know if it will work but I need to know if the pill is effective cuz I'm freaking out.